This invention relates to a process for producing an inorganic barium-containing solids composition suitable as an additive in fired clay products, the water-insoluble products obtainable according to the invention which can be used as additives for producing fired clay products, their use in the production of fired clay products and the clay products produced using the additives obtainable according to the process of the invention.
Barium sulfide leaching is a process step in the production of barium compounds. The starting material is the naturally-occurring mineral heavy spar (barite). Heavy spar contains approximately 92 to 98% by weight barium sulfate and additionally varying quantities of calcium salts and iron salts and also silicate. The ground heavy spar is mixed with finely ground coal and reduced to barium sulfide at high temperatures (approx. 1,200.degree. C.). The cooled, solidified molten mass containing barium sulfide is extracted with hot water, forming barium sulfide lye. The barium sulfide lye obtained in this barium sulfide leaching is further reacted, for instance to form barium carbonate, which is used in the glass industry.
In barium sulfide leaching, a residue remains. This residue, which, if it is not dried, occurs as a water-containing sludge, contains in addition to some coal predominantly barium salts, and also calcium salts. These are present in particular in the form of carbonates, sulfur compounds and silicates. These leaching residues have hitherto been disposed of. However, this is ecologically undesirable and additionally constitutes a waste of valuable potential raw materials.
A known problem in the production of fired clay products, for instance bricks, is that if the clay and/or other materials, such as mixing water, needed for producing fired clay products contain sulfate, undesired bloom (efflorescence) and discoloration of the fired clay occur. It is already known that the addition of a small quantity of pure barium carbonate prevents the formation of such blooms. The barium carbonate is used in technically pure form, i.e. having a degree of purity of approximately 95% by weight or higher, and is added to the dry or moist clay which has not yet been fired. Production of the barium carbonate with this degree of purity is expensive.